System and method for managing projector bulb life

ABSTRACT

Projector bulb life is managed to achieve desired performance parameters, such as a maximum life mode or maximum brightness mode, by sensing bulb luminance and applied the sensed luminance with a luminance feedback controller to drive the bulb to achieve the desired performance parameter. For instance, in maximum life mode the luminance feedback controller reduces power applied to the bulb to restrict bulb luminance to a maximum luminance setpoint when greater luminance is available with a newer bulb. In maximum brightness mode, the luminance feedback controller increases power applied to the bulb to increase bulb luminance if the sensor senses luminance below a threshold due bulb wear. Bulb life management improves project image illumination to display information in a variety of projector types, including digital mirror devices and liquid crystal displays.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to the field of informationdisplay, and more particularly relates to a system and method formanaging projector bulb life.

2. Description of the Related Art

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

Often a primary objective of information handling systems is the displayof information to users as an image. Conventionally information has beendisplayed with cathode ray tube (CRT) devices that generally direct anelectron beam towards phosphors located in a screen to form images ofthe information for viewing by users. CRT devices typically apply chromafeedback to control electrical drive signals and thus manage the qualityof images generated by the impact of electrons on the phosphor screen.However, obtaining high resolution images from CRT displays is difficultand often involves the use of bulky devices with relatively high powerconsumption. Primarily as a result of the generally large size of CRTdevices, consumers have turned to projector devices for the display ofinformation images. Generally, projector devices display information byilluminating an image with high intensity light to present the image ona screen. For instance, digital mirror device (DMD) projectors, alsoknown as digital light processor (DLP) projectors, direct high intensitylight at an image generator having a large number of miniature mirrorsthat selectively direct the light at a screen to form an image. Anotherexample of a projector device is a liquid crystal device (LCD or LCOS)projector that directs high intensity light through a LCD screen havingthe desired image which is then projected onto a screen.

Projector devices have substantially improved the display of informationcompared with CRT devices by providing better resolution with largerimages so that consumers have turned to projector devices with increasedfrequency. For instance, graphics projectors initially developed to makepresentations with applications running on portable information handlingsystems have now become a common selection for home theaters that showDVD movies. Similarly, DMD and LCD projectors have become anincreasingly common selection for consumer television sets. Onedifficulty that remains with consumer acceptance of projector displaydevices is that the projector bulbs typically used in projector devicesare expensive ultra high pressure mercury vapor or xenon halogen lampsthat have a generally short life span of approximately 1500 hours.Consumers are hesitant to invest in projector display devices for commonhome entertainment use where the projector display devices requirefrequent replacement of expensive bulbs. Consumers are also hesitant toinvest in projector display devices that have perceived performanceproblems, such as decreased available brightness as a projector bulbages. As a bulb ages, the arc gap of the bulb increases so that agreater voltage is required to generate the same level of luminance fromthe bulb. Eventually, the arc gap increases to a distance that resultsin reduced brightness to half or less of a bulb's original brightness sothat the consumer has to replace the bulb with a new bulb to obtainacceptable brightness performance.

SUMMARY OF THE INVENTION

Therefore a need has arisen for a system and method which managesprojector bulb output parameters in order to obtain desired brightnessand length of life performance.

In accordance with the present invention, a method and system areprovided which substantially reduce the disadvantages and problemsassociated with previous methods and systems for managing a projectorbulb life. A luminance feed back control loop senses luminance output bya projector bulb and provides a control signal to the projector bulb'spower driver to maintain brightness output from the bulb so that thebulb has a desired performance, such as maximum life or maximumbrightness over the bulb's life.

More specifically, a bulb is illuminated by a power driver that providesvariable power to the bulb to generate variable brightness to illuminateinformation formed as an image, such as with a DMD or LCD displaydevice. Bulb brightness is sensed by a luminance sensor and provided toa luminance feedback controller as a sense signal, such as a voltage.The luminance controller generates an error control signal that is fedback to the power driver to compensate for changes in bulb performanceover time, such as arc length induced bulb brightness changes related tobulb aging. The luminance controller manages bulb luminance to obtaindesired bulb performance parameters. In a maximum life mode, theluminance controller restricts bulb brightness to a threshold value byreducing the power provided to the bulb so that a new bulb with greateravailable brightness illuminates at a lower brightness level to reducewear on the bulb. In a maximum brightness mode, the luminance controllerincreases bulb brightness to a threshold value by increasing powerprovided to the bulb so that an older bulb with degraded availablebrightness illuminates at a greater brightness level. In an unmanagedmode, the luminance controller is disengaged to allow a user to manuallyselect a desired brightness.

The present invention provides a number of important technicaladvantages. One example of an important technical advantage is thatconsumers are presented with an information image from a projector withimproved consistency in the brightness of the image. Consumers areprovided with improved life of a projector's bulb and face reduced costin the replacement of projector bulbs through the control of the powerthat drives a bulb based on feedback of the luminance output by thebulb. The control algorithm allows a user to select between bulbperformance goals so that the user can have maximum availableillumination from a new bulb or initially reduced illumination below abulb's maximum available brightness as a tradeoff for longer bulb lifeand improved performance from the bulb as the bulb ages.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features and advantages made apparent to those skilled in theart by referencing the accompanying drawings. The use of the samereference number throughout the several figures designates a like orsimilar element.

FIG. 1 depicts a block diagram of a luminance feedback controller;

FIG. 2 depicts a graph of examples of projector bulb performanceparameters;

FIG. 3 depicts a digital mirror device configured manage bulbperformance parameters; and

FIG. 4 depicts a liquid crystal display configured to manage bulbperformance parameters.

DETAILED DESCRIPTION

Projector bulb life management enhances the display of information, suchas that generated by an information handling system, by illuminating animage having the information with a luminance designed to achievedesired bulb performance parameters, such as maximized life or maximizedbrightness over the life of a bulb. For purposes of this disclosure, aninformation handling system may include any instrumentality or aggregateof instrumentalities operable to compute, classify, process, transmit,receive, retrieve, originate, switch, store, display, manifest, detect,record, reproduce, handle, or utilize any form of information,intelligence, or data for business, scientific, control, or otherpurposes. For example, an information handling system may be a personalcomputer, a network storage device, or any other suitable device and mayvary in size, shape, performance, functionality, and price. Theinformation handling system may include random access memory (RAM), oneor more processing resources such as a central processing unit (CPU) orhardware or software control logic, ROM, and/or other types ofnonvolatile memory. Additional components of the information handlingsystem may include one or more disk drives, one or more network portsfor communicating with external devices as well as various input andoutput (I/O) devices, such as a keyboard, a mouse, and a video display.The information handling system may also include one or more busesoperable to transmit communications between the various hardwarecomponents.

Referring now to FIG. 1, a block diagram depicts a luminance feedbackcontrol loop 10 operable to achieve desired projector bulb performanceparameters, such as maximized bulb life or maximized bulb brightness. Aprojector bulb 12 provides illumination for display of information basedon the level of power provided by a power driver 14. Brightness for bulb12 is selectable by a user through a user brightness selector 16, whichmanually controls the power applied to bulb 12 by power driver 14. Aluminance sensor 18 is disposed proximate to bulb 12 to sense theluminance provided by bulb 12 and output a sense signal proportional tothe sensed luminance, such as a voltage provided by a voltage convertercircuit. The voltage output by luminance sensor 18 is compared with asetpoint voltage by luminance controller 20 to generate a differencesignal amplified as an error signal and fed back to power driver 14 in aclosed-loop feedback form. The voltage output to bulb 12 by power driver14 is thus increased or decreased depending on the sign and magnitude ofthe error signal from luminance controller 20. Luminance controller 20applies a control algorithm to provide a desired projection bulbluminance that achieves a desired projection bulb performance parameter,such as maximum life or maximum brightness over the life of bulb 12. Inalternative embodiments, other feedback signals may be used, such ascurrent, duty cycle or other lamp-input parameters that define a controlerror correction signal.

Luminance controller 20 alters the power applied to bulb 12 by powerdriver 14 to compensate for changes in bulb luminance over a bulb'slife. Generally, error correction signals impact bulb luminance outputwhen user brightness selector 16 calls for a high brightness that isclose to or at the maximum brightness of bulb 12. With newer bulbs,luminance controller 20 tends to decrease the output of power driver 14so that luminance output by bulb 12 decreases in a tradeoff thatincreases the overall life of bulb 12. With older bulbs, luminancecontroller 20 tends to increase the output of power driver 14 so thatluminance output by bulb 12 increases in a tradeoff that decreases theremaining life of bulb 12. The error signal correction provided byluminance controller 20 depends in part on the type of projector bulbperformance parameter selected by a user through a selector switch 22.In a maximum life position, luminance controller 20 applies an algorithmthat restricts power applied from power driver 14 so that sensedluminance does not exceed a threshold value. In a maximum brightnessposition, luminance controller 20 applies an algorithm that increasespower applied from power driver 14 so that sensed luminance does notfall below a threshold value when a user has selected a brightnesssetting of greater than a predetermined intensity. In an unmanagedposition, the switch opens to disengage luminance controller 20 frommanagement of bulb 12.

Referring now to FIG. 2, a graph compares projector bulb performancewith maximum life, maximum brightness and unmanaged luminance feedbackmodes. Solid line 24 depicts expected luminance performance of anunmanaged bulb from an initial high intensity to an end of lifeintensity of approximately 50% of the initial intensity. Dashed line 26depicts managed luminance performance of a bulb to achieve maximumbrightness over the life of the bulb. Initially, luminance controller 20allows the bulb to provide the same luminance intensity as in theunmanaged mode. However, when the luminance intensity reaches a setpointvalue, luminance controller 20 provides an error correction controlsignal that increases the output of power driver 14 so that theluminance sensed with luminance sensor 18 is maintained substantially atthe setpoint value for the life of the bulb. Dotted line 28 depictsmanaged luminance performance of a bulb to achieve maximum life. In themaximum life mode, luminance controller 20 provides an error correctioncontrol signal that restricts the output of power driver 14 so that theluminance sensed with luminance sensor 18 does not exceed a setpointvalue that is substantially lower than the unmanaged maximum luminanceintensity of the bulb. By initially driving a new bulb less hard, thebulb provides the setpoint value for a greater amount of time withluminance controller 20 gradually increasing the output of power driver14 as the brightness of the light provided by the bulb decreases overtime. Both the maximum brightness and maximum life bulb performancecontrol modes obtain bulb luminance output greater than the 50%end-of-life level for longer time periods by forcing greater powerthrough the bulb as the bulb wears over time. In the embodiment depictedby FIG. 2, the maximum brightness and maximum life intensity setpointsare substantially equal, although in alternative embodiments optimizedbrightness and life for different types of bulbs may be achieved withdifferent setpoints for each mode and various thresholds around eachsetpoint.

Referring now to FIG. 3, a digital mirror device 30 is depictedconfigured to manage bulb performance parameters with luminance feedbackcontroller 20. Bulb 12 sends light through a main aperture 32 and into acolumnator 34 that directs the light via a mirror 36 to an imagegenerator 38. An infrared filter 40 filters out infrared light and acolor wheel 42 spins to provide red, green and blue light to imagegenerator 38. The intensity of the brightness of bulb 12 is determinedby the power provided from power driver 14 as corrected with the controlsignal from luminance feedback controller 20 in order to provide adesired bulb performance, such as maximum life or maximum brightness.Luminance feedback controller generates its error control signal basedon sensed luminance of bulb 12 taken from one or more luminance sensorsdisposed along the path of the light provided by bulb 12. One luminancesense location is provided with a second aperture 44 formed near bulb 12or in columnator 34. Other luminance sense locations are provided bymeasuring the level of infrared light filtered at infrared filter 40,measuring the level of light that impacts color wheel 42, or measuringthe light that leaks at mirrors associated with image generator 38. Inalternative types of projectors, alternative locations for light sensorsmay be selected. For instance, as is depicted by FIG. 4, a liquidcrystal display projector has luminance sensors located at a blue lightfilter 46 or at the liquid crystal display 48 that generates the imagefor display of desired information.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

1. A system for managing projector bulb life, the system comprising: aluminance sensor disposed to sense the luminance of the projector bulb;a luminance controller interfaced with the luminance sensor and a powerdriver of the projector bulb, the luminance controller operable toreduce the power driver output to limit projector bulb luminance at orbelow a setpoint level associated with a desired projector bulb life ifthe maximum luminance of the projector bulb is greater than apredetermined brightness.
 2. The system of claim 1 wherein the luminancecontroller is further operable increase power driver output to maintainprojector bulb luminance substantially at the setpoint level if thesensed luminance falls to a predetermined brightness.
 3. The system ofclaim 1 further comprising a switch disposed between the power driverand the luminance controller, the switch operable to selectively disablethe projector bulb luminance controller interface with the power driver.4. The system of claim 1 wherein the projector bulb comprises an ultrahigh pressure mercury vapor bulb.
 5. The system of claim 1 wherein theprojector bulb comprises a xenon halogen bulb.
 6. The system of claim 1wherein the luminance sensor comprises an infrared sensor associatedwith an infrared filter of the projector.
 7. The system of claim 1wherein the luminance sensor comprises a visible light senor aligned tosense light leakage from a mirror of the projector.
 8. A method formanaging projector bulb life, the method comprising: sensing theluminance of the projector bulb; determining that the sensed luminanceexceeds a luminance threshold associated with a desired projector bulblife; and reducing the power applied to the projector bulb to reduce theluminance of the projector bulb to at or below the luminance thresholdassociated with the desired projector life.
 9. The method of claim 8further comprising: determining that the sensed luminance falls below aluminance threshold associated with a minimum desired availableluminance at a maximum brightness setting; and increasing the powerapplied to the projector bulb to increase the luminance of the projectorbulb to the luminance threshold of the minimum desired luminance for themaximum brightness setting.
 10. The method of claim 9 wherein theluminance threshold associated with a desired projector bulb life andthe luminance threshold associated with minimum desired availableluminance are substantially equal when the projector is set at maximumbrightness.
 11. The method of claim 8 further comprising engaging aswitch to override the reducing of the power applied to the projectorbulb so that the luminance exceeds the threshold.
 12. The method ofclaim 8 further comprising: passing the light from the projector bulbthrough an infrared filter; wherein sensing the luminance furthercomprises sensing the infrared light at the infrared filter.
 13. Themethod of claim 8 further comprising: passing the light from theprojector bulb through a first aperture to a colmunator for illuminatingan image; passing the light from the projector bulb through a secondaperture to a luminance sensor for sensing the luminance.
 14. The methodof claim 8 wherein the bulb provides light for a digital mirror deviceprojector having a color wheel, and wherein sensing the luminancefurther comprises sensing luminance at the color wheel.
 15. The methodof claim 8 wherein the bulb provides light for a digital mirror deviceprojector having a mirror for projecting an image, and wherein sensingthe luminance further comprises sensing luminance of light leakage atthe mirror.
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